Injection molding apparatus

ABSTRACT

An injection molding apparatus which enables easier monitoring of the nozzle touch condition from the outside of a clamping unit (70). A stationary platen (10) of the clamping unit (70) is furnished with monitoring holes (16a, 16b). The monitoring holes (16a, 16b) extend from at least either of the front and rear sides of the clamping unit (70) toward a locating hole (12) into which a sprue bush (51) of dies is located. The monitoring holes (16a, 16b) may be interlocked with shutters (22a, 22b) which are opened or closed in response to open or close motion of the purge shield (20). Furthermore, it is possible to provide windows (34a, 34b) in a purge shield (30) so as to allow an operator to look into the monitoring holes (16a, 16b) therethrough.

TECHNICAL FIELD

The present invention relates to an injection molding apparatus, moreparticularly to an injection molding apparatus equipped with a clampingand an injection units disposed opposite to each other.

BACKGROUND ART

In the injection molding apparatus equipped with a clamping and aninjection units disposed confronting each other, injection is performedby causing the tip of the nozzle of the injection unit to abut againstthe dies fixed to the clamping unit. When the dies have been changed,the cylinder assembly of the injection unit has been changed, or whenthe injection unit has been turned for change of the parts, it isnecessary to check, at the time of the nozzle touching operation,whether the tip of the nozzle of the injection unit accurately abutsagainst the sprue bush of the dies while operating the injection unitmanually or at a low speed.

For this purpose, the abutment between the sprue bush and the injectionnozzle tip, i.e. the condition of nozzle touch, is conventionallymonitored through a clearance formed in the vicinity of the purge shieldby an operator looking into the front side of the stationary platen (asurface on the side of the injection unit) from the front side of theclamping unit. However, a point where the sprue bush and the injectionnozzle tip abut each other tends to locate in a dark place far inwardfrom the front side of the stationary platen. Thus, it has beendifficult for the operator to accurately monitor the condition ofabutment.

This difficulty increases as the size of the injection molding apparatusincreases, since the size of the stationary platen also increasesaccordingly. Thus, there has been a possibility of having the resinleaked outside due to improper nozzle touch.

DISCLOSURE OF INVENTION

The present invention provides an injection molding apparatus renderingeasier for an operator to monitor abutting condition between the spruebush and the injection nozzle tip.

According to the present invention, an injection molding apparatuscomprises a clamping unit having a movable platen and a stationaryplaten. The stationary platen has a locating hole into which the sprueof dies is to be located, and at least one monitoring hole extendingfrom the side thereof toward the locating hole, so that the locatinghole can be monitored from the side of the clamping unit through thismonitoring hole.

The direction of the monitoring hole is determined so that an operatoris allowed to monitor the locating hole from at least either of thefront and rear sides of the clamping unit.

The monitoring holes may be provided with shutters, the shutters beinginterlocked with a purge shield so that the monitor hole is openedtogether with the purge shield when the purge shield is opened. Thisshutter prevents the gas or resin from blowing off directly toward anoperator during the purge operation.

Furthermore, a window may be provided in the purge shield covering thefront side of the stationary platen. The window of the purge shield andthe monitoring holes are designed to cooperatively allow the operator tomonitor the locating hole even during the purge operation of theclamping unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a partly sectional side view showing an injection moldingapparatus in accordance with a first embodiment of the presentinvention;

FIG. 2 is a front view showing a stationary platen of the injectionmolding apparatus shown in FIG. 1;

FIG. 3 is a horizontal sectional view taken along a line III--III ofFIG. 2;

FIG. 4 is a side view showing the stationary platen shown in FIG. 2;

FIG. 5 is a transversal sectional view showing an essential part of aninjection molding apparatus in accordance with a second embodiment ofthe present invention;

FIG. 6 is a transversal sectional view showing an essential part of aninjection molding apparatus in accordance with a third embodiment of thepresent invention; and

FIG. 7 is a perspective view showing a purge shield shown in the thirdembodiment of FIG. 6.

BEST MODE FOR CARRYING OUT THE INVENTION

An injection molding apparatus in accordance with the first embodimentof the present invention will be explained with reference to FIGS. 1-4.In FIG. 1, a clamping unit 70 and an injection unit 80 are disposed on abase 60 confronting each other. The clamping unit 70 includes a movableplaten 40, a stationary platen 10 and dies 50 disposed therebetween. Aninjection nozzle 81 of the injection unit 80 has a tip to be broughtinto contact with a sprue 51 of the dies 50 when performing injectionmolding.

As shown in FIGS. 2 and 3, the stationary platen 10 has a locating hole12 opening at a central portion thereof on the side close to the movableplaten 40 (i.e. a rear side). The main body 14 of the stationary platen10 includes a guide wall 15, which protrudes on the side of theinjection unit 80 (in the forward direction), and the guide bore 13 isformed in the guide wall 15. The guide bore is gradually taperedbackward until it comes to communicate with the locating hole 12. Theguide wall 15 is provided with two monitoring holes 16a and 16b, theformer being a through hole extending from the front side with respectto an operator's position and the latter being a through hole extendingfrom the side opposing the above front side.

The monitoring hole 16a extends straight from the outside of the guidewall 15 toward the locating hole 12 until it reaches the guide bore 13.The monitoring hole 16a has a diameter large enough to allow an operatorto look into the locating hole 12 entirely through this monitoring hole16a from the front side of the clamping unit 70. The monitoring hole 16bprovided at the rear side is substantially identical in constructionwith the monitoring hole 16a provided at the front side except that theyare symmetrically disposed.

Several lightening holes 17 are provided around the guide wall 15 toreduce the weight of the stationary platen 10. A reference numeral 18represents a hole for installing a tie bar.

Upon setting of the dies 50 into the stationary platen 10, the spruebush 51 of the dies 50 is positioned inside the locating hole 12. Thus,the monitoring holes 16a and 16b enable an operator to monitor thepositional relationship between the tip of the injection nozzle 81 ofthe injection unit 80 and the sprue bush 51, i.e. the nozzle touchcondition during the nozzle touch operation. In this case, the operatorcan monitor the nozzle touch condition from either the front side or therear side of the clamping unit 70 through the monitoring hole 16a or16b. Furthermore, provision of a plurality of monitoring holes will makeit easier to monitor the abutting condition between the sprue bush 51and the injection nozzle 81, because light is introduced inside througha monitoring hole not being used by an operator.

By the way, the condition of abutting between the sprue bush 51 and theinjection nozzle 81 can be adjusted by using a jack bolt or a lateralposition adjusting bolt (not shown) provided in the injection unit 80 bychanging the mutual position between the sprue bush 51 and the injectionnozzle 81.

Next, a second embodiment of the present invention will be explainedwith reference to FIG. 5. The stationary platen 10 is provided with aplaten cover 19, on which there are provided two door plates 21a and 21bof a purge shield 20 and two shutters 22a and 22b for the monitoringholes 16a and 16b. The door plates 21a and 21b are supported on thefront side of the platen cover 19 at their base ends so as to berotatable about hinges 23, 23 provided thereon; thus, the guide bore 13can be covered (closed) on both the front and rear sides. Although notshown in the drawing, there is provided a top board extending on thedoor plates 21a and 21b. Overall configuration of the purge shield 20 isa rectangular shape with an open bottom when seen from the front.

The shutters 22a and 22b are provided on the platen cover 19 in such amanner that the platen cover 19 is partly replaced by the shutters 22aand 22b at the portions where phantom lines extending from themonitoring holes 16a and 16b intersect with the platen cover 19,respectively. Each of the shutters 22a and 22b is swingably supported bya hinge 24.

The door plates 21a and 21b of the purge shield 20 are connected withthe shutters 22a and 22b by means of thin links 25, 25, respectively.When the door plates 21 take a closed position in which each door plateis normal to the front side of the platen cover 19, the shutters 22respectively become flush with the surface of the front plate of theplaten cover 19. That is, the monitoring holes 16a and 16b are closed.In general, the purge shield 20 is equipped with limit switches (notshown) for detecting open conditions of the door plates 21a and 21b,respectively. These limit switches function to prevent the injectionunit from performing purge operation.

With above arrangement, only when the door plates 21a and 21b of thepurge shield are opened, i.e. only when the limit switches are activatedin response to the opening of the door plates 21a and 21b to disable theinjection unit from performing the purge operation, the shutters 22a and22b are opened to allow an operator to look into the monitoring holes16a and 16b. Thus, the operator is surely protected from being directlyexposed to purged resin or gas while monitoring the abutting conditionbetween the sprue bush 51 and the injection nozzle 81. Furthermore,during the purge operation, not only the door plates 21a and 21b of thepurge shield 20 but the shutters 22a and 22b are closed, so that neitherthe gas nor the resin will not leak out of the purge shield 20 duringthe purge operation.

Next, a third embodiment of the present invention will be explained withreference to FIGS. 6 and 7. The stationary platen 10 is provided with aplaten cover 19'. A purge shield 30 is attached to a front side of theplaten cover 19'.

The purge shield 30 consists of a main body 31 and a lid member 32, andits overall configuration is of a truncated pyramid whose top facesforward. As shown in FIG. 7, the purge shield 30 has a top board 33,although neither a rear board nor a bottom board is provided. The lidmember 32 constitutes one of side surfaces of the above truncatedpyramid and has a window 34a of a transparent synthetic resin board. Thelid member 32 is attached to the front surface of the platen cover 19'by the hinges 35 so that the lid member is allowed to swingably turnfrontward about the hinges. The main body 31 has a front plate 38 whichincludes an opening 37 to allow a front edge of the cylinder assembly 20to enter. A side plate 38 has a window 34b similar to the window 34a.The main body 31 is attached to the front side of the platen cover 19'by hinges 39 so as to be swingable toward the rear side about thehinges.

The purge shield 30 is formed to be large enough to allow phantom linesextending from the monitoring holes 18a and 16b to intersect with thewindows 34a and 34b. (Refer to FIG. 6)

The above arrangement enables an operator to monitor the abuttingcondition between the sprue bush 51 and the injection nozzle 81 from thewindows 34a and 34b through the monitoring holes 16a and 18b even if theinjection unit 20 is in a purge operation.

The present invention is not limited to the embodiments disclosed by thedrawings. For example, the monitoring holes 16a and 16b may be providedonly in the front side of the clamping unit 70. Furthermore, in thesecond embodiment, if the door plates 21a and 21b of the purge shieldhave sizes as large as covering the monitoring holes 16a and 16b whenopened, the door plates 21a and 21b themselves may be made oftransparent material so that an operator become able to look into themonitoring holes 16a, 16b through the transparent door plates 21a, 21b.Furthermore, in the same embodiment, the links 25, 25 may be omitted,and the shutters 22a and 22b of the purge shield 20 can be made oftransparent material so as to allow an operator to look into themonitoring holes through these transparent windows.

The present invention enables an operator to perform the nozzle touchoperation while monitoring the abutting condition between the sprue bushof the dies and the nozzle tip of the injection unit. Thus, the nozzletouch operation can be performed accurately. Even if the thickness ofthe stationary platen increases, the monitoring of the nozzle touchoperation can be done easily. Furthermore, the nozzle touch operationcan be monitored without the danger of being exposed to the purged gasand resin during the purge operation and the gas and resin are preventedto leak outside through the monitoring holes during the purge operation.

We claim:
 1. An injection molding apparatus comprising:a clamping unit,for holding dies therebetween, comprising:a movable platen, and astationary platen; said stationary platen comprising:a first hole,serving as a locating hole, into which a sprue of the dies is located,and a second hole, serving as a monitoring hole, extending from a sideof said stationary platen toward said first hole, whereby the first holeof said stationary platen is monitored from the side of the clampingunit through said second hole, wherein said second hole extends from theside of the stationary platen, which confronts an operator position, tothe opposite side of the stationary platen and slopes toward saidlocating hole.
 2. An injection molding apparatus in accordance withclaim 1, wherein said clamping unit further comprises:a platen coversurrounding said stationary platen; and a purge shield,mounted to saidplaten cover between said operator position and said stationary platenand being selectively opened and closed, said platen cover having ashutter facing to said second hole, and said shutter being opened andclosed in response to opening and closing motions of said purge shield,whereby said first hole is monitored through said second hole when saidshutter is opened.
 3. An injection molding apparatus in accordance withclaim 1, wherein said clamping unit further comprises a purge shielddisposed between said operator position and said stationary platen,saidpurge shield provided with a window, whereby said first hole ismonitored through said window of the purge shield and said second hole.4. An injection molding apparatus in accordance with claim 3, whereinsaid clamping unit comprises a platen cover surrounding said stationaryplaten, and said purge shield is attached to said platen cover.
 5. Aninjection molding apparatus in accordance with claim 1, furthercomprising a plurality of second holes which serve as monitoring holes.6. An injection molding apparatus comprising:a clamping unit, forholding dies therebetween, comprising:a movable platen, and a stationaryplaten; said stationary platen comprising:a first hole, serving as alocating hole, into which a sprue of the dies is located, and a secondhole, serving as a monitoring hole, extending from a side of saidstationary platen toward said first hole, whereby the first hole of saidstationary platen is monitored from the side of the clamping unitthrough said second hole; a platen cover surrounding said stationaryplaten; and a purge shield mounted to said platen cover between saidoperator position and said stationary platen and being selectivelyopened and closed, said platen cover having a shutter facing to saidsecond hole, and said shutter being opened and closed in response toopening and closing motions of said purge shield, whereby said firsthole is monitored through said second hole when said shutter is opened.